If you have ever paused mid-sentence wondering whether to write theirs or their’s, you are not alone. This is one of the most searched grammar questions online and the confusion is completely understandable. English possessive rules can feel inconsistent, and that apostrophe temptation is real.
By the end of this guide, you will know exactly when to use theirs or their’s, why the mistake happens, and how to avoid it forever in emails, essays, social media, and everyday writing.
Theirs or Their’s – Quick Answer
The answer is simple: “theirs” is correct. “Their’s” is always incorrect.
“Theirs” is a third-person plural possessive pronoun. Like other possessive pronouns his, hers, ours, yours, its it never takes an apostrophe.
| Form | Correct? | Example |
| Theirs | ✅ Yes | That book is theirs. |
| Their’s | ❌ No | ~~That book is their’s.~~ |
The rule is universal. There is no dialect, style guide, or regional English where their’s is accepted. If your grammar checker flags it, trust the flag.
Theirs
“Theirs” is a possessive pronoun. It stands alone replacing a noun to show that something belongs to a group of people or a singular person of unspecified gender.
Key traits of “theirs”:
- Replaces a noun (does not come before one)
- Indicates ownership by a third party
- Works for plural or singular gender-neutral subjects
- Never followed by a noun directly
Examples of correct usage:
- The victory was entirely theirs.
- I finished my report; they’re still working on theirs.
- The house on the corner is theirs.
- Someone left a bag is it theirs?
Their
“Their” is a possessive adjective (also called a possessive determiner). Unlike theirs, it always comes before a noun to modify it.
Examples of correct usage:
- They packed their bags.
- The students submitted their assignments on time.
- Their dog barks all night.
| Word | Function | Position in Sentence |
| Their | Possessive adjective | Before a noun |
| Theirs | Possessive pronoun | Replaces a noun |
A quick test: if a noun follows the word, use their. If it replaces the noun entirely, use theirs.
The Origin of Theirs or Their’s
Understanding where theirs comes from helps explain why their’s never belonged in the language to begin with.
The word “their” entered English around 1200 CE, borrowed from Old Norse þierra, meaning “of them.” It replaced the Old English form hiera. By around 1300 CE, “theirs” had emerged as a double possessive formed by adding the possessive suffix -s to “their,” on the analogy of his, hers, and ours.
Crucially, English possessive pronouns developed independently of the apostrophe convention. Apostrophes were introduced into English writing around the 16th century to mark omitted letters in contractions not to signal possession in pronouns. By the time apostrophes became common, possessive pronouns like his, hers, theirs, and ours were already firmly established without them.
This is why theirs or their’s is never a genuine debate in historical or formal grammar: the apostrophe version simply never existed in standard written English.
British English vs American English Spelling
One common question around theirs or their’s is whether British and American English differ on this point. They do not.
| Variety | Correct Form | Notes |
| American English | theirs | No apostrophe |
| British English | theirs | No apostrophe |
| Australian English | theirs | No apostrophe |
| Canadian English | theirs | No apostrophe |
Both the Oxford English Dictionary (used as the British standard) and Merriam-Webster (the American standard) list only theirs no apostrophe, no exceptions.
If you write for a global audience whether in the US, UK, India, Canada, or Australia the rule stays the same: theirs is always correct, and their’s is always wrong.
Which Spelling Should You Use?
The answer to theirs or their’s is never up for debate: use theirs, every single time, in every context.
Here is a practical decision guide:
- Formal writing (essays, reports, cover letters) → theirs
- Informal writing (texts, social posts, chats) → theirs
- Academic writing → theirs
- Professional emails → theirs
- Creative writing → theirs
There is no situation formal or casual, British or American where their’s is appropriate. If you find yourself typing the apostrophe, delete it.
Memory trick: Compare it to his. You would never write hi’s, so do not write their’s.
Common Mistakes with Theirs or Their’s
The confusion around theirs or their’s is predictable. Here is why people get it wrong and how to stay on the right side of it.
Mistake 1: Adding an apostrophe because it “looks like possession”
English uses apostrophe + s to show possession for nouns (the dog’s bone, Maria’s car). Writers sometimes apply this logic to pronouns but possessive pronouns are a separate category and never use apostrophes.
- ❌ The decision was their’s.
- ✅ The decision was theirs.
Mistake 2: Confusing “their’s” with “it’s”
It’s (with apostrophe) is a contraction of it is. Writers see that pattern and assume their’s must work the same way. It does not. Its (no apostrophe) is the possessive form of it and similarly, theirs is the possessive form with no apostrophe needed.
Mistake 3: Mixing up their, there, and they’re
These three homophones trip up even experienced writers:
| Word | Type | Meaning | Example |
| their | Possessive adjective | Belonging to them | Their car is new. |
| there | Adverb/pronoun | Place or existence | It’s over there. |
| they’re | Contraction | They are | They’re coming tomorrow. |
| theirs | Possessive pronoun | Something belonging to them | That house is theirs. |
Mistake 4: Writing “theirs'” (apostrophe after the s)
Some writers overcorrect and write theirs’. This is also incorrect. There is no apostrophe before or after the s in theirs.
Theirs or Their’s in Everyday Examples
Seeing theirs in real sentences is the fastest way to make the rule stick. Here are 12 practical examples across different contexts:
Everyday speech:
- I cooked dinner. The dessert is theirs to deal with.
- We brought our chairs. Those belong to theirs.
Workplace writing:
- The project outcomes were theirs from start to finish.
- The credit for the campaign is entirely theirs.
Academic writing:
- The responsibility to cite sources is theirs.
- Both teams submitted essays, but theirs scored highest.
Formal correspondence:
- The property records confirm the land is theirs.
- The decision, in this instance, is theirs alone.
Casual digital writing:
- lol that typo is totally theirs, not mine
- omg is that dog theirs??
Gender-neutral singular usage:
- Someone left their jacket I’ll hold it until it’s clear whose it is. If no one claims it, I’ll assume it’s theirs.
Theirs or Their’s – Google Trends & Usage Data
Search data tells an interesting story about how often people look up theirs or their’s. According to Google Trends analysis, this query consistently spikes at the start of academic terms particularly in September and January when students return to essay writing and grammar rules come back into focus.
The top countries searching for theirs or their’s include the United States, India, the United Kingdom, Canada, and the Philippines reflecting how widely English is used as a second language and how universal this grammar confusion is.
Key insight from usage data:
| Search Intent | What Users Want |
| “theirs or their’s correct” | Quick answer (covered above) |
| “theirs vs their’s grammar” | Rule explanation |
| “is their’s ever correct” | Confirmation it is not |
| “their’s with apostrophe” | Clarification on apostrophe rule |
The data confirms this is not a niche question millions of writers at every level encounter this confusion each year.
Keyword Variations Comparison
Writers and editors searching for guidance on theirs or their’s often use a variety of related search terms. Here is how the key variants compare:
| Keyword Variation | Correct Form | Notes |
| theirs or their’s | theirs | Core confusion |
| their’s or theirs | theirs | Same question, reversed order |
| is their’s a word | No | Their’s is not a real word |
| theirs possessive pronoun | theirs | Formal grammar context |
| theirs apostrophe rule | theirs | Apostrophe should not be added |
| their vs theirs difference | Both | Their (adjective) vs theirs (pronoun) |
| theirs meaning | theirs | Belongs to them |
| possessive pronoun no apostrophe | theirs, his, hers, ours, yours | All follow the same rule |
Understanding these variations helps writers recognize the rule applies across a whole family of pronouns not just theirs or their’s in isolation.
Conclusion
When it comes to theirs or their’s, the rule is refreshingly clear in an otherwise complicated language: theirs is always correct, and their’s is always wrong.The confusion persists because English usually does use apostrophes to mark possession but possessive pronouns are the exception to that rule. His, hers, its, ours, yours, and theirs all indicate ownership without an apostrophe, and they always have.
Whether you are writing a formal report, a quick email, a university essay, or a social media caption, the answer to theirs or their’s never changes. Drop the apostrophe, trust the rule, and move on with confidence.The next time you hesitate between theirs or their’s, just ask: would I write hi’s instead of his? The answer is no and neither would you write their’s instead of theirs.
